This invention relates to intravenous infusion sets (IV sets) of the gravity feed type, and more particularly to such sets including electronic control systems for establishing the drip rate and monitoring said rate to detect alarm conditions. Even more specifically, this invention relates to improvements in the electronically controlled IV set disclosed in copending LeFevre Application Ser. No. 492,280, assigned to the same assignee as the present invention, and now abandoned in favor of Application Ser. No. 637,206, filed Dec. 3, 1975.
The prior art includes numerous means for controlling the rate of flow through IV sets for regulating the rate of intravenous administration of fluid to a patient. The rate, for example, may be controlled manually by adjusting a mechanical clamp on the IV tubing while counting drops falling in the drip chamber over a predetermined period of time to achieve a desired drop rate. Electronic controls have been developed to eliminate this time consuming and error prone manual procedure. Such systems generally include a valve operating within or upon the IV tubing and a circuit for controlling the valve to establish a desired flow rate. Many of such circuits also incorporate drop detectors for sensing a drop forming or falling in the drip chamber. While the electronic IV controls known heretofore have generally represented a considerable improvement over prior manual techniques, they have not been altogether successful in allowing an attendant to precisely select a drip rate and thereafter precisely maintaining such rate. For example, it has been common to select the flow rate in electronic IV sets using conventional dial type selectors, such an approach having an inherent accuracy limitation. Further, some prior art devices operate flow control valves at some multiple frequency of a desired drop rate, in order to control the flow rate through the set.
Problems also exist in the prior art with regard to alarm systems associated with the electronic control. In some cases, the alarm systems may be made "hair trigger" responsive, causing an alarm upon the detection of only a single error or missed drop. In other cases a deadband is established in which errors may occur without causing an alarm. The former systems are prone to premature alarm conditions, especially at high flow rates where the occasional error may be tolerated. The latter systems may be found to be too insensitive, especially at low flow rates.